Roger Burman, head of Winterhill school, Rotheram, with some of his year 11 pupils. Photograph: David Sillitoe for the Guardian

When Winterhill came into being nine years ago, it faced serious challenges. It was the product of an unhappy merger between two schools in the Kimberworth area of Rotherham – one of which was in special measures – and little was expected of its 1,240 pupils, many of whom hailed from some of the most deprived areas of the country.

No wonder Roger Burman, Winterhill's barrel-chested headteacher, was beaming on Thursday morning as he welcomed a line of nervous teenagers into the school hall, some of whom confessed they had been awake since 5am ("and I usually get up at 1pm", giggled Amy Jones as she loitered outside).

Dressed in flip-flops and jeans, muscles bursting out of his light blue shirt, Burman was celebrating the fifth consecutive year of improving results, with 90% of students achieving five A*s to C – 62% including English and Maths. When Burman took over seven years ago, that figure was "in the 40s". As we talked, one boy interrupted to give the head a hug: "I got an A in core science, sir!"

"Not one of our pupils this year will leave year 11 with nothing," said Joanne Cater-Whitham, one of the deputy heads.

"Even one lad who came to us with almost no English, a month before exams, has come away with one D. It's a difficult catchment area, but the staff are 100% determined that they all achieve their potential.

"For a lot of our students, getting five Cs is a massive achievement, but it's what they need to get into college. The distance many need to travel to get there is enormous."

For almost a quarter of Winterhill's students, English is a second language, while 58% of pupils are poor enough to qualify for free school meals. In recent years the school has taken in 100 eastern European children, many Slovakian and Romanian Roma, who bring with them extra challenges.

"Some can't afford their own uniforms or pencil tins and we have to teach them the most basic things, like how to queue up for dinner," said Cater-Whitham.

Kamol Meesri, a slight 16-year-old with spiky black hair, looked over the moon."I got a C in English, I can't believe it," he said. Kamol moved to Rotherham seven years ago from Thailand when his mum married a local man, and could barely speak a word of English on arrival. "English was always a difficult subject for me, but I knew I needed to get a C to go to college."

Nearby, English teacher Stephanie Noonan hovered by Bradley Nelson as he opened his envelope. "Thank god," he said, seeing he'd managed Cs in both English and maths. "I'm buzzing, Miss," he said, adding that he didn't want to go to college, but planned to get a job in engineering.

"Yours were the first results I looked for, Bradley," Noonan told him, confiding later that he was somewhat "hit or miss" in the classroom.

"He was always more bothered about his image than his grades, but he knew he needed those Cs and he was predicted a D in English so has done really well."

Michael Buchanan, 16, was delighted to do better than he expected, and particularly to get As in his sciences. "I'm really happy," he said. "This I what I needed to make the next step to college."

Winterhill does not just aim to get pupils over the five Cs threshold, but tries hard to get the best out of their most able students too. This year's star performer was Bethany Harcourt, a cheery girl with long red curls, who had bagged seven A*s to go with the A* in maths she got last year when she took the exam early. She hopes to one day be either a paediatric oncologist or a surgeon - "I'm not sure yet." But on Thursday, her only plan was to celebrate. "My parents have promised to take me to Nando's," she said.